乳腺癌中增强子RNA的生成及其作用的分子机制研究

Breast cancer is among the most common cancer types observed in women worldwide, with its notoriously high mortality being a serious health issue. Recently, the number of reported cases of breast cancer has increased dramatically in China. One of the major causes of cancer development in human mammary gland is the aberrant transcriptional activation of a cohort of genes involved in cell proliferation, among others, which is induced by unbalanced levels of estrogen. Through state-of-art genome-wide sequencing techniques, it was reported recently that estrogen not only induces estrogen receptor (ERα)-mediated transcriptional activation of coding genes, but also a new class of non-coding RNA named enhancer RNA (eRNA), which is defined primarily based on the site of its production, ERα-bound enhancers, in breast cancer cell lines, such as MCF7. Intriguingly, the expression levels of enhancer RNA correlate strongly with that of its neighboring estrogen-targeted coding genes, and functional studies suggest that enhancer RNA is involved in the transcriptional activation of coding genes. However, the molecular mechanisms governing eRNA transcription/production, and eRNA function in the regulation of its corresponding coding genes remain incompletely understood. Numerous studies support the functional significance of epigenetic regulators, including histone/DNA/RNA-modifying enzymes (writer), enzymes removing (eraser) and factors recognizing (reader) such modifications, in transcriptional regulation of both coding genes and non-coding RNAs. Therefore, epigenetic regulators have been shown to involve in the development of multiple types of cancers and other human diseases, becoming one of the most targeted protein families for drug development. The current proposed study aims to elucidate the critical players involved in the production of eRNA by large-scale and unbiased screening based on the large protein family of epigenetic regulators. Furthermore, we aim to address the molecular mechanisms underlying the regulation of transcription of estrogen-target genes by eRNA, establishing a regulatory axis composed of estrogen, epigenetics regulator, eRNA and estrogen-targeted coding genes, with eRNA at its center. Finally, screening and optimization of small molecules targeted to components in the identified molecular axis, and further validation of their efficacy and specificity will be done by using cell-based assays and animal-based breast cancer models. To summarize, our ultimate goal is to reveal novel components in the estrogen-mediated signaling pathway, which could be potentially serving as drug targets for the prevention and treatment of breast cancer.

乳腺癌是全球女性人群中最常见且致死率最高的癌症之一,而中国又是乳腺癌发病率增长最快的国家之一。乳腺癌变的重要诱因之一是由于雌激素紊乱而导致的其靶基因转录异常激活;同时雌激素也能诱导一类新的非编码RNA(增强子RNA)的转录激活,该类非编码RNA参与其邻近雌激素靶基因转录调控。细胞内转录事件往往受到表观遗传调控子的精密调控。表观遗传调控子大家族被证实与多种癌症密切关联,并已成为最热门的药物靶点之一。本课题拟通过对常见表观遗传调控子的筛选,探寻对乳腺癌中增强子RNA的生成起调控作用的关键因子,并进一步阐述增强子RNA参与雌激素靶基因调控的分子机制,建立一条以雌激素、表观遗传调控子、增强子RNA、雌激素靶基因为轴心的分子通道,以期多角度地揭示新的乳腺癌诊疗标志物和靶点 ,课题后期将进一步探寻并优化靶向所揭示靶点的活性小分子,并通过细胞和动物实验加以验证,为将来的临床试验和药物开发奠定基础。

乳腺癌是全球女性人群中最常见且致死率最高的癌症之一，而中国又是乳腺癌发病率增长最快的国家之一。乳腺癌变的重要诱因之一是由于雌激素紊乱而导致的其靶基因转录异常激活。最近研究发现雌激素也能诱导大量非编码RNA的产生，其中一些已被证实与乳腺癌密切关联。本项目集中研究了雌激素诱导的一类新型非编码RNA增强子RNA（enhancer RNA，eRNA）的生成及其作用分子机制。通过对表观遗传调控子家族的筛选，我们发现组蛋白去甲基化酶JMJD6是调节雌激素和雌激素受体诱导的增强子RNA产生，邻近编码基因的转录激活和乳腺癌细胞生长和肿瘤形成的重要调节因子，并且这些功能和JMJD6的酶活性密切相关，表明JMJD6是可用于治疗雌激素受体阳性乳腺癌的潜在药物靶点；在阐述JMJD6调控增强子及其增强子RNA激活的过程中，我们发现JMJD6能直接与RNA结合，进一步研究发现JMJD6和可变剪接因子U2AF65相互作用，并且广泛调节基因可变剪接事件，揭示了JMJD6参与疾病特别是癌症发生发展的一个新颖机制；同时，在研究雌激素和雌激素受体调控的基因转录激活过程中，我们通过高通量测序系统地鉴定了受雌激素诱导的非编码谱，并对其中的环状RNA（circRNA）和长非编码RNA（lncRNA）展开研究。总之，项目申请团队自获得该重大研究计划（培养项目）的资助以来，在乳腺癌中增强子RNA的生成及其作用的分子机制研究方面取得了一系列研究成果，很好的完成了研究计划。本项目揭示了雌激素诱导的增强子RNA的关键调控因子以及其参与调控的分子机制，建立一条以雌激素、表观遗传调控子、增强子RNA、雌激素靶基因为轴心的分子通道，多角度地揭示新的乳腺癌诊疗标志物和靶点。同时，本项目揭示了表观遗传调控子组蛋白去甲基化酶的一个新颖功能：参与基因的可变剪接，有助于真正地解析其参与疾病发生发展的分子机制。对雌激素诱导的其它非编码RNA的系统鉴定和功能研究为探寻新的乳腺癌药物靶点提供了新的思路和途径。